Cubia, .hack//Quarantine (aka Vol.4).
GODS, I hated fighting that thing after it came out of left field partway in.
HAHAHAH dood when i SAW this topic. I didnt' even click it yet. but i IMMIDIATELY Thought of Cubia as well. and SURE enough i click on the show latest post option and the FIRST WORD i see is Cubia hahah ohhh Cubia what a SoB i swear.
Yeah, Cubia was a pain in the axe. It didn't help that I was expecting Tarvos at the time, either.
Of course, now that I'm ON Tarvos, I hate the impaled serpent very, very much. Immunity-swapping, Nice Boat-load of hits required to Data Drain, and on top of that . . . 1HKO. It has a 1HKO cinematic.
Also, not quite a boss and not NEARLY the same game . . . my first time fighting Zappa in GGXX (arcade).
I was completely unprepared for Raou to pop up out of nowhere and start OWNING ME TO DEATH. Now I know to kill him with speed, but that first time is definitely disconcerting.